Device for vacuum-pressing of DVD substrates

ABSTRACT

The invention relates to a device for vacuum-pressing of disk-shaped substrates, in particular DVD substrates into a finished DVD, wherein the device has a vacuum chamber with two substrate holders and an intermediate element that can be displaced inside the vacuum chamber; and wherein the intermediate element divides the vacuum chamber into a first low-pressure chamber and a second chamber that can be alternatingly connected to vacuum or to an overpressure, which makes the device particularly suited for use with a hot-melt thermoplastic adhesive.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of prior filed copending U.S. applicationSer. No. 10/226,095, filed Aug. 22, 2002, which is a continuation ofprior filed copending PCT International application no. PCT/EP01/01979,filed Feb. 21, 2001 and which claims the priority of German PatentApplication Serial No. 100 08 111.8, filed Feb. 22, 2000, pursuant to 35U.S.C. 119(a)-(d).

FIELD OF THE INVENTION

The invention relates to a device for vacuum pressing of disk-shapedsubstrates, in particular DVD substrates into a finished DVD, and moreparticularly to a device that uses a hot-melt thermoplastic adhesive.

BACKGROUND OF THE INVENTION

Various conventional machines apply vacuum and pressure to joindisk-shaped substrates, such as DVD substrates, by using both hot-meltadhesives and UV-curable varnishes. UV-curable varnish requires asmaller pressure than hot-melt adhesive. Also, with UV-curable varnish,the superpositioned substrates still float on top of each other as longas the UV varnish is not cured by exposing it to UV radiation.Conversely, with a hot-melt adhesive, the position of the substrates isimmediately fixed in upon contact and can no longer be adjusted.

DE 197 15 779 A1 describes a method for joining two DVD substrates witha UV varnish by inserting one of the substrates in the cover section andthe other substrate in the bottom section of a vacuum chamber and fixingthem in a centered position, and by placing the cover section on thebottom section with the adhesive layers opposing one another. After thevacuum chamber is evacuated and the pressure has decreased below apredetermined pressure, a centering/clamping device disposed in thecover section is released and the upper substrate falls onto the lowersubstrate, whereby the falling motion is reinforced by several weightswhich are arranged in the cover section around the central hole of thesubstrate and provided with axial guide rods. Springs and the like canbe provided instead of weights. When the two adhesive layers of thesubstrates are then positioned on top of each other with the adhesivelayers still wet, the vacuum chamber is vented to air, whereby theatmospheric pressure causes those areas between the adhesive and the twosubstrates that have not yet made contact to be pressed against eachother. This arrangement is not suitable for gluing substrates with anapplied hot melt adhesive, because the weights and the atmosphericpressure cannot generate the pressing force required for preciselyjoining the substrates. In addition, the contact pressing force producedby the weights is not distributed uniformly across the entire substratesurface.

JP 1-204727 A suggests producing optical data carriers by coating twosubstrates with an adhesive of the hot-melt type and subsequentlyjoining the two substrates in a vacuum chamber, whereby certain upperlimit values for pressure, temperature and pressing force are preset. Awall in the vacuum chamber has openings for piston rods which can beused to press the pressure plates against each other, with thesubstrates placed between the pressure plates.

EP 0 735 530 A1 describes a system where the DVD substrates haveinitially an adhesive of the hot melt type (thermoplastic adhesive)spread across their surfaces. Subsequently, a UV-curable liquid adhesiveis filled in a recess provided proximate to the central hole in onesubstrate. The substrate that has only hot melt adhesive applied, isthen rotated by a handling system by 180°, so that the sides of thesubstrates having the applied adhesive face one another, and placed onthe lower substrate. In this joined state, the two substrates and/or theDVD are placed onto a lower pressure plate which has in its center aquartz glass window for admitting UV radiation, and which also forms thebottom plate of a vacuum chamber. The cover section of the vacuumchamber is moved from the top position downwardly, until the edge of thecover contacts the bottom plate, thereby forming a chamber, which can beevacuated through a connection disposed in the bottom plate. The pistonrod of a piston-cylinder unit passes through the cover. Another pressureplate is located on the lower end of the piston rod. When the pressurein the vacuum chamber drops below a predetermined pressure, the pressureis applied to the upper piston rod which moves the piston rod downwardlyand presses the superpositioned substrates together between the upperpressure plate and the bottom plate. At the same time, UV light isintroduced through the quartz glass window into the vacuum chamber tocure the UV adhesive. After a time that can be preset, the vacuumchamber is vented to air, the piston is moved downwardly and the UVirradiation is tuned off. This concludes the process step of joining thesubstrates and the completed DVD can be removed.

These conventional systems for joining DVD substrates have thedisadvantage that the vacuum chamber, on one hand, and the pressingdevice, on the other hand, are implemented as separate units and areoperated independent of each other. As a result, the pressure plateswhich press the substrates against each other are always restrictivelyguided, so that a small tilt in the position of the substrates cannot beeasily compensated. When such small tilt in the position of thesubstrate occurs, a very high pressing force is applied at one locationand a rather lower pressing force is applied at another location. Thisimpairs the parallel alignment of the DVD.

The German utility model DE 299 04 325 U1 describes a device for joiningDVD substrates by applying a vacuum. This reference provides acollapsible chamber, whereby one substrate is inserted in the coversection and the other substrate in the bottom section of the vacuumchamber. The substrate holder which is located in the bottom portion ismovably supported. In addition, a lifting plate is provided, from whichseveral guide shafts extend upwardly through the bottom portion of thevacuum chamber. The guide shafts are operatively connected with thelower substrate holder so as to enable an additional mechanicaldisplacement of the lower substrate holder for increasing the pressingforce. When a low-pressure is applied between the substrates, in a firststep, the lower moveable substrate holder moves upwardly and thesubstrates are glued together with a first value of the pressing force.In a second step, the lifting plate is moved upwardly and mechanicallydisplaces via the a guide shafts the lower substrate holder, therebyincreasing the pressing force to a second value. However, the guideshafts have to be disadvantageously guided vacuum-tight through thebottom portion of the vacuum chamber, which requires complex sealingmeasures. Moreover, at least the lifting plate and the guide shafts mustdisadvantageously be moved downwardly by the joining vacuum due to themechanical connection with the lower substrate holder. Consequently, thedrive means for the lifting plate have to be mechanically decoupled fromthis lifting plate, or the drive means has to also be moved downwardlyby the joining vacuum. This system also restrictedly guides thesubstrates due to the guide shafts and the lifting plate. This devicetherefore has the same disadvantages as the conventional devicesdescribed above.

It is desirable to provide a device for vacuum pressing of DVDsubstrates, which allows for relative alignment of the substrates to beglued. The device should preferably have a relatively simpleconstruction and the pressing force employed for joining and pressingthe DVD substrates should preferably be continuously adjustable across awide range.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a device for vacuum-pressingof disk-shaped substrates, in particular of DVD substrates, includes avacuum chamber; a first substrate holder for a first substrate housed inthe vacuum chamber and formed as an intermediate element dividing thevacuum chamber into a first low-pressure chamber and a secondoverpressure chamber. The intermediate element can be displaced in thevacuum chamber and is equipped with a peripheral seal. The devicefurther includes a second substrate holder for a second substrate housedin the vacuum chamber. The intermediate element, on a side facing thelow-pressure chamber, is formed as a first substrate support for thefirst substrate. The second substrate holder has a second substratesupport for the second substrate that is disposed in the vacuum chamberopposite the first substrate support.

The process flow during vacuum pressing can thereby be optimized bycontrollably adjusting, on one hand, the low-pressure and, on the otherhand, the overpressure, whereby the intermediate element is pulled inwhen the vacuum is applied, causing a decrease in volume of thelow-pressure chamber, which pulls the substrates against each other. Theprocess flow can be further optimized by building up additional pressurein the overpressure chamber at an appropriate time, whereby theintermediate element and thereby also one of the substrates are pressedsufficiently strongly against the other substrate. Since theintermediate element is supported only by the seal(s) and is thereforefloating to some extent, the intermediate element can perform a smalltilting motion, allowing the substrate holder of the intermediateelement to conform within certain limits to the position of the othersubstrate. It should be noted that the molded substrates do not haveexactly the same thickness across their surface area, so that regionsare formed that are subjected to a high pressing force, where the otherregions are subjected to a lower pressing force.

According to another aspect of the invention, a device forvacuum-pressing of disk-shaped substrates, in particular of DVDsubstrates, includes a vacuum chamber and a first substrate holder for afirst substrate housed in the vacuum chamber and formed as anintermediate element dividing the vacuum chamber into a firstlow-pressure chamber connected to a vacuum pump and a second chamberthat can be alternatingly connected to the vacuum pump and a compressedgas source. The intermediate element can be displaced in the vacuumchamber and is equipped with a peripheral seal. A second substrateholder for a second substrate is also housed in the vacuum chamber. Theintermediate element on a side facing the first chamber is formed as afirst substrate support for the first substrate. The second substrateholder has a second substrate support for the second substrate disposedin the vacuum chamber opposite the first substrate support.

By connecting the lower chamber selectively and alternatingly to acompressed air source and a vacuum pump, a vacuum can be produced onboth sides of the intermediate element. When the same vacuum pressure isapplied on both sides, then there is a force equilibrium and theintermediate element initially remains in its initial position. When acertain value of the low-pressure is reached, the pressure in the lowerchamber is raised to ambient pressure, which causes the intermediateelement to move upwardly and the substrates to contact each other.Subsequently, the system is switched over to an overpressure to enable areliable pressing operation. The joining speed of the process can beoptimized by adjusting the rate at which the pressure in the lowerchamber is raised. Depending on the joining speed, the joining processcan be adjusted to be rather hard or rather soft, which is important forbrittle or sensitive layers, such as DVD 18, DVD-R and DVD-RW.

Advantageous embodiments of the invention may include one or more of thefollowing features. The device can include pressure generating means forgenerating a pressure on at least one of the first and second substrateholders, such as a vacuum pump and a compressed gas source. Theintermediate element can be formed as a piston having at least twospaced annular grooves, with the peripheral seal having at least twospaced apart sealing rings inserted in the corresponding annulargrooves.

The intermediate element further can be made of several sections,wherein at least two sections are provided with a peripheral seal. Theseal can include one or more sealing lips. The section forming aboundary between the first low-pressure chamber and the second chamberis formed as the first substrate holder. Several rods can be disposedbetween the sections.

The intermediate element can further include circumferentially arrangedsliding or roller bearings, enabling the intermediate element to move inthe vacuum chamber. The first low-pressure chamber can include a coversection being secured on the vacuum chamber by a hinge, to enableopening and closing the cover section. The cover section may furtherinclude an axially displaceable centering pin for centering the secondsubstrate, wherein the centering pin can be inserted through the secondsubstrate into a center hole provided in the first substrate when thefirst substrate is positioned on the first substrate holder.

Advantageously, at least one of the substrate holders can be implementedas a vacuum plate which can include vacuum channels for holding thesubstrates by vacuum-suction. The vacuum channels can be operatedseparately of each other. The cross sectional area of the vacuumchannels disposed near the center of the substrate holders is greaterthan the cross sectional area of the vacuum channels near the peripheralregion of the substrate holders. The vacuum channels can also beconnected to a compressed gas source, wherein the compressed gas canblow at least one of the substrates off a corresponding substrate holderfrom a center of the substrate towards the periphery of the substrate.The vacuum channels located near the center of the substrate holders canbe operated separately from the vacuum channels located near theperiphery of the substrate holder. An O-ring can surround eithersubstrate for providing a seal.

The vacuum chamber, in particular the second chamber, can have eitherseparate connections or a single connection from which a connecting linebranches off, for alternatingly connecting the second chamber to thevacuum pump and the compressed gas source.

Further features and advantages of the present invention will beapparent from the following description of preferred embodiments andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWING

The following figures depict certain illustrative embodiments of theinvention in which like reference numerals refer to like elements. Thesedepicted embodiments are to be understood as illustrative of theinvention and not as limiting in any way.

FIG. 1(a)-FIG. 1(m) show schematically an exemplary device for vacuumpressing of substrates at various stages of the process;

FIG. 2 is an enlarged view of the device for vacuum pressing ofsubstrates at the process stage depicted in FIG. 1(i);

FIG. 3 is a first embodiment of the exemplary device for vacuum pressingin an open position;

FIG. 4 is a top view of the device of FIG. 3; and

FIG. 5 is a second embodiment of the exemplary device for vacuumpressing in an open position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is directed to a device for vacuum-pressing of substrates,in particular DVD substrates.

Referring first to FIG. 1, a vacuum chamber 1 includes a bottom section2 for receiving a first (A) substrate 3 and a cover section 4 forreceiving a second (B) substrate 5. The vacuum chamber can be closed byrotating the cover section 4 about an axis 6 that is perpendicular tothe plane of the drawing sheet. First, the DVD substrates 3 and 5, towhich an adhesive has been applied, are inserted in the cover sectionand the bottom section (FIG. 1 a), with the surface having the adhesivepointing upwardly. The substrates are positioned in the bottom sectionand the cover section on vacuum plates and are fixed in their positionby the vacuum (holding vacuum). In the next step of the process (FIG. 1b), the holding vacuum on the A-substrate 3 and the holding vacuum onthe B-substrate 5 are switched off, the centering pins 7 and 8 areextended so as to pass through the corresponding center hole of thesubstrates. Thereafter, the holding vacuum on the B-substrate 5 isturned on again (FIG. 1 c), the B-centering pin 8 is retracted (FIG. 1d), the cover section 4 is rotated about the axis 6 and the vacuumchamber 1 is closed (FIG. 1 e). To prevent the substrates from beingpulled against each other due to electrostatic charges, the holdingvacuum on the A-substrate 3 is turned on again when the vacuum chamberis closed. After the vacuum chamber is closed, the B-centering pin 8 isextended, passing through the center opening of the A-substrate 3,whereby the A-centering pin 7 is simultaneously pushed back (FIG. 1 f).Both DVD substrates A and B are now centered together on the B-centeringpin 8. The joining vacuum is now applied, i.e., the vacuum chamber 1 isevacuated with the vacuum pump, causing the joining plate A, i.e.,substrate holder 9, to be pulled upwardly by the vacuum (FIG. 1 g). Toprovide support, compressed air is applied to the substrate holder 9from below (FIG. 1 h). When the lower substrate holder 9 with theA-substrate 3 has come within a certain distance of the B-substrate 5,the holding vacuum is switched off on both substrates A and B, and airis admitted to the substrates A and B through the vacuum channels in thesubstrate holders. Both substrates A and B are then blown off thesubstrate holders (FIG. 1 i), which will be described in more detailbelow with reference to FIG. 2. Since neither substrate A and B isconnected to the vacuum plates shortly before contact between theadhesive surfaces is established, the substrates can once more beprecisely centered via the common centering pin. When the substrates areblown off, they are bent in the middle from the inside to the outside(see also FIG. 2), so that the adhesive surfaces establish contact fromthe inside towards the outside, whereby the joining vacuum between thesubstrates A and B also removes the residual air between the substrates.The substrates A and B are now joined; the substrate holder 9 (see FIG.3) which is formed as a piston reaches a stop, and the desired pressure(FIG. 1 j) can build up under the piston. When the pressing force hasbeen applied for a sufficiently long time, the B-centering pin 8 isretracted, the holding vacuum A is switched on and the joining vacuum isswitched off (FIG. 1 k). As soon as the pressure is switched off, thepiston can retract, the blow-off at B is switched on and the A-centeringpin is extended (FIG. 11). Finally, the cover section 4 is rotated inthe open position and the holding vacuum A is switched off. Thecompleted DVD is centered on the substrate holder 9 (the plate A) andcan now be removed.

FIG. 2 is an enlarged view of the process step 1 i. Vacuum channels 11to 13 are disposed in both substrate holders 9 and 10, with the mainchannels 11 which are each connected to a vacuum pump extendinghorizontally in the substrate holders 9 and 10. Channels 12 branch offthe main channels 11 proximate to the center hole, whereas channels 13branch off the main channels 11 in the peripheral region and terminatein the surface of the substrate holders. The channels 12 have a largerdiameter that the channels 13. This system of channels helps form theholding vacuum in the process steps depicted in FIG. 1. By switchingfrom vacuum to blow-off, air is also admitted via this channels systemin the process step depicted in FIG. 1 i for blowing off the substratesA and B in the center. The substrates are centered by the B-centeringpin 8, which passes through both center holes. The lower substrateholder 9 has a sufficiently large opening for the B-centering pin 8. Byblowing off the substrates A and B, the substrates are released from thesurface of the substrate holders and can be centered exactly once morebefore the adhesive-coated surfaces make contact with each other. Thesubstrates are preferably released and blown off first on the inside dueto the larger vacuum bore 12 on the inside. Releasing and blowing offthe substrate from the inside outside significantly reduces the risk ofair inclusions between the substrates A and B. Alternatively, the innerand outer channels 12 and 13, respectively, can be separated, as shownin the example of FIG. 5, so that the vacuum on the outside can beswitched off with a delay by a separate valve and can be switched overwith a delay for blowing off the substrates. When the vacuum channels 12and 13 are operated separately (see FIG. 5), then the vacuum channels 12and 13 can have the same diameter. Holdings the substrates at themarginal regions can be supported by using upper and lower O-rings. Byseparately forming and controlling the vacuum channels in the uppersubstrate holder 10 and in the lower substrate holder 9, differentblow-off pressures P1 and P2 can be set, whereby a different dishing canbe defined to counteract or compensate for existing dishing effects.

FIG. 3 shows the vacuum chamber 1 in an open position, with substrates Aand B (reference numerals 3 and 5) inserted in the bottom section 2 andthe cover section 4, as well as with the centering pins 7 and 8. Alsoseen in the bottom section and the cover section are the vacuum channels11, 12 and 13 for the holding vacuum and the blow-off feature. It canalso be seen that the lower substrate holder 9 is formed as a piston,which is floatingly, but sealingly, supported by an upper sealing lip 14and a lower sealing lip 15 for displacement in the bottom section 2. Theguide means 25 can be provided in the region of the upper sealing lip.Otherwise, the piston 9 is spaced apart from the interior wall of bottomsection. In this way, the floating piston 9 can optimally adapt to thestationary cover. When the vacuum chamber is closed and sealed with asealing ring 18, a two-chamber system is formed whereby above the piston9 a low-pressure chamber 20 is formed having a forming vacuum and belowthe piston 9 an overpressure chamber 19 is formed which is operativelyconnected with a compressed air source 21 (not shown). The lowersubstrate holder 9 is drawn in by the forming vacuum in the low-pressurechamber 20 and suctioned against the upper substrate holder 10. In theprocess steps depicted in FIGS. 1 h to k, air is introduced into theoverpressure chamber 19 and the lower substrate holder 9 is movedupwards by this compressed air. A mechanical misalignment during thepressing operation is eliminated by guiding the piston 9 only in itsupper range and otherwise connecting the piston 9 with the interior wallonly by the sealing lips 14 and 15. When the lower substrate holder orpiston 9 reaches a stop, the required pressure can be applied to thepiston 9 via the overpressure chamber 19, so as to complete the joiningprocess with a pressing step.

FIG. 4 shows a top view of the vacuum chamber 1 in an open position.Identical reference numerals describe identical elements.

Since the adhesive of the hot melt type is free of solvents and meltsand becomes tacky at high temperatures, the substrate holder 9 and/or 10as well as the cover section and/or the bottom section of the vacuumchamber can be heated to shorten the time between the joining operationand the cooling step.

In the second embodiment of the joining station according to theinvention illustrated in FIG. 5, the lower chamber 19 is connected toboth a compressed air source 21 and a vacuum pump 24 and canalternatingly be filled with compressed air or evacuated. For reducingthe amount of air entrained between the substrates as much as possiblebefore joining, a high vacuum is required in the joining space 20between the substrates. A high joining vacuum reduces air inclusionsbetween the adhesive-covered surfaces of the substrates. This improvesthe quality of the glued surface as well at the adhesion, which resultsin an improved stability and flatness of the bonded disk. For achievinga high joining vacuum of approximately 50 mbar and below, the lowerchamber 19 is initially also connected to a vacuum pump 24 and alsoevacuated. In other words, an identical vacuum pressure is applied toboth sides of the piston 9. The low-pressure chamber 20 (=joining vacuumchamber) and the lower chamber 19 have the same diameter. Accordingly,the forces are balanced and the piston 9 initially remains in itsinitial position. When the desired vacuum is reached on both sides ofthe piston 9, the pressure in the lower chamber 19 is raised to ambientpressure, allowing the piston to move upwardly due to the pressuredifference. Subsequently, the system is switched over to the compressedair source 21 and the substrates are pressed together as shown in theexample of FIG. 3. The joining speed, i.e., the speed at which thepiston 9 moves upwardly, can be optimized for the process by adjustingthe speed at which the pressure is raised from vacuum to ambientpressure. The joining process can be adjusted to be rather hard orrather soft by adjusting the joining speed, which is important forbrittle or delicate layers, such as DVD 18, DVD-R, and in DVD-RW. In allother aspects, the construction and the functionality are identical tothose of the embodiment of FIG. 3. Identical reference numerals describeidentical elements.

To facilitate joining of the two substrates from the inside to theoutside, the upper substrate 5 is initially slightly curved with thehelp of the upper centering pin 8, which has for this purpose a suitableshoulder. Then the vacuum on the inner vacuum channels 12 is switchedoff. Thereafter, the vacuum on the outer vacuum channels 13 is switchedoff. Optionally, additional vacuum channels 26 can be provided in thecenter region of the substrate, which can preferably be connected withthe inner vacuum connection. A soft support for the substrates, forexample PAI, facilitates joining from the inside to the outside. Afterthe inner vacuum is switched off, the system can optionally be switchedover to blow-off.

Positioning and orientation of the substrates A and B relative to oneanother can be improved by mechanically interlocking the cover section 4with the bottom section 2 after the joining station is closed.

While the invention has been disclosed in connection with the preferredembodiments shown and described in detail, various modifications andimprovements thereon will become readily apparent to those skilled inthe art. Accordingly, the spirit and scope of the present invention isto be limited only by the following claims. What is claimed as new anddesired to be protected by Letters Patent is set forth in the appendedclaims and their equivalents:

1. A device for vacuum-pressing of disk-shaped substrates, in particularof DVD substrates, comprising: a vacuum chamber; a first substrateholder for a first substrate housed in the vacuum chamber and formed asan intermediate element dividing the vacuum chamber into a firstlow-pressure chamber connected to a vacuum pump and a second chamberthat can be alternatingly connected to the vacuum pump and a compressedgas source, said intermediate element displaceable in the vacuum chamberand being equipped with a peripheral seal; and a second substrate holderfor a second substrate housed in the vacuum chamber, wherein theintermediate element on a side facing the first chamber is formed as afirst substrate support for the first substrate, and wherein the secondsubstrate holder has a second substrate support for the second substratedisposed in the vacuum chamber opposite the first substrate support. 2.The device according to claim 1, wherein the vacuum chamber comprisesseparate connections for connecting the second chamber alternatingly tothe vacuum pump and the compressed gas source.
 3. The device accordingto claim 1, wherein the vacuum chamber comprises a single connectionfrom which a connecting line branches off, for connecting the secondchamber alternatingly to the vacuum pump and the compressed gas source.4. The device according to claim 1, wherein the intermediate element isformed as a piston having at least two spaced annular grooves and theperipheral seal comprises at least two spaced apart sealing ringsinserted in the corresponding annular grooves.
 5. The device accordingto claim 1, wherein the intermediate element includes a plurality ofsections, wherein at least two sections are provided with a peripheralseal, with the section, which seals against the first low-pressurechamber, formed as the first substrate holder; and a plurality of rodsdisposed between the plurality of sections.
 6. The device according toclaim 1, the intermediate element further comprising circumferentiallyarranged sliding or roller bearings enabling displacement of theintermediate element in the vacuum chamber.
 7. The device according toclaim 1, wherein the seal further includes at least one sealing lip. 8.The device according to claim 1, wherein the first low-pressure chamberincludes a cover section being hingedly secured on the vacuum chamber toenable opening and closing the cover section.
 9. The device according toclaim 8, wherein the cover section further includes an axiallydisplaceable centering pin for centering the second substrate, with thecentering pin being insertable through the second substrate into acenter hole provided in the first substrate when the first substrate isdisposed on the first substrate holder.
 10. The device according toclaim 1, wherein at least one of the first and second substrate holdersis implemented as a vacuum plate.
 11. The device according to claim 1,wherein at least one of the first and second substrate holders includesvacuum channels for holding the first and second substrates byvacuum-suction.
 12. The device according to claim 11, wherein the vacuumchannels disposed in the first substrate holder and the second substrateholder can be operated separately from each other.
 13. The deviceaccording to claim 11, wherein the vacuum channels disposed proximate toa center hole of the first and second substrates have a larger crosssection than the vacuum channels disposed in a peripheral region of thefirst and second substrate holders.
 14. The device according to claim11, wherein at least one of the first and second substrates includes anO-ring surrounding the substrate.
 15. The device according to claim 11,wherein the vacuum channels can be connected to a compressed gas source,with a compressed gas being blown through the vacuum channels when thevacuum-suction is switched off.
 16. The device according to claim 15,wherein the compressed gas blows at least one of the first and secondsubstrates off a corresponding substrate holder from a center of thesubstrate towards the periphery of the substrate.
 17. The deviceaccording to claim 11, wherein the vacuum channels disposed near acenter of the at least one of the first and second substrate holders canbe operated separately from the vacuum channels disposed near aperiphery of the substrate holder.
 18. A device for vacuum-pressing ofdisk-shaped substrates, in particular of DVD substrates, comprising: avacuum chamber; a first substrate holder for a first substrate housed inthe vacuum chamber and formed as an intermediate element dividing thevacuum chamber into a first chamber connected to a vacuum pump and asecond chamber connected to a compressed gas source, said intermediateelement displaceable in the vacuum chamber and being equipped with aperipheral seal; and a second substrate holder for a second substratehoused in the vacuum chamber, wherein the intermediate element on a sidefacing the first chamber is formed as a first substrate support for thefirst substrate, and wherein the second substrate holder has a secondsubstrate support for the second substrate disposed in the vacuumchamber opposite the first substrate support, wherein at least one ofthe first and second substrate holders includes vacuum channels forholding the first and second substrates by vacuum-suction, wherein afirst plurality of vacuum channels are disposed proximate to a centerhole of the first and second substrates and have a cross section whichis greater than a cross section of a second plurality of vacuum channelswhich are disposed in a peripheral region of the first and secondsubstrate holders.